— 469 —
Therefore to fix their Species, a real Essence is supposed.       §49. To avoid this therefore, they have supposed a real Essence
belonging to every Species, from which these Properties all flow, and
— 470 —
would have their name of the Species stand for that. But they not
having any Idea of that real Essence in Substances, and their Words
signifying nothing but the Ideas they have, that which is done by
this Attempt, is only to put the name or sound, in the place and
stead of the thing having that real Essence, without knowing what
the real Essence is; and this is that which Men do, when they speak
of Species of Things, as supposing them made by Nature, and
distinguished by real Essences.
Locke Hum III, 6, §49, pp. 469-470